(1) Field of the Invention
This invention relates to an improved positive type photosensitive material and a process for developing the same, and more particularly to a photosensitive reproduction material which is able to give an excellent color-developed positive relief image by developing the exposed photosensitive material with an aqueous alkali solution and washing it with water.
(2) Description of the prior art
In the past, the following processes have been employed to obtain a positive relief image using ultraviolet rays as a light source.
(1) A layer of photosensitive composition consisting of o-quinonediazide derivative and alkali soluble resin binder (e.g. novolak resin) is formed on a base material to obtain a photosensitive reproduction material. The photosensitive reproduction material thus obtained is exposed and the exposed areas are alkali-developed.
(2) A layer of photosensitive composition consisting of a reaction product of p-diazodiphenylamine with phosphotungstic acid and a vinylidene chloride-acrylonitrile copolymer binder is formed on a base material to obtain a photosensitive reproduction material. The photosensitive reproduction material thus obtained is exposed and exposed areas are developed by using or water-alcohol solution (see Japanese patent publication No. 42-14326, claiming priority of U.S. Appln. Ser. No. 345,848 filed Feb. 19, 1964).
(3) A layer of photosensitive composition consisting of an ethylenically unsaturated compound, a thermoplastic polymer, a photopolymerization initiator, and a dye or pigment is formed between two support sheets to obtain a photosensitive reproduction material. The photosensitive reproduction material thus obtained is subjected to a development/peel procedure utilizing the change of adhesive strength in the exposed areas, and a relief image is formed by the remaining photosensitive composition (see (U.S. Pat. No. 3,060,023).
However, these prior art processes have the following disadvantages and are insufficient to provide images having high density and high resolving power.
That is, in the above-mentioned process (1), the binder resin can not be dyed without difficulty. Further, it is difficult to combine the binder resin with an efficient color developing mechanism. For this reason, a dye or pigment is usually dispersed in the binder resin and, in order to obtain high light shielding density, a long period of exposure is necessary and practically disadvantageous.
In the above-mentioned process (2), high light shielding density can be obtained without decreasing sensitivity by providing a light shielding layer on the photosensitive layer which is formed on a transparent base material, but in this case exposure can be made only from the transparent base material side and the decrease of resolving power due to the thickness of the base material is unavoidable.
Further, the above-mentioned process (3) has the same disadvantage as process (2), because exposure is made through the transparent base material. Additionally, since development is made by agglutination and destruction of the photosensitive layer, the resolving power is lower. Another disadvantage in the process (3) is the high price of the photosensitive material.